Ocean, nature, critters, and recreation

May 02, 2012

Pacific gray whales experience significant baby boom

The Pacific gray whale population received a significant and much-needed boost this season, which is evident by the remarkable number of calves passing California on their first-ever journey to Arctic home waters.

Through Tuesday volunteer spotters at Point Vicente had logged 181 calf sightings, making this the third-highest season since the project began in 1984. The record high of 222 was tallied in 1997.

It's too early to know whether this will be a record-setting year, but it will be one of the top calf-production years since spotting stations were established, beginning with the ACS-LA project.

At Point Piedras Blancas in Central California, NOAA Fisheries biologist Wayne Perryman, director of the Cetacean Health and Life History Program, said his team counted 28 cow-calf pairs on two days during the past two weeks.

Twenty-eight is the most for a single day since 2004, when 456 calves were counted by the end of what turned out to be the second-biggest production season since the program began in 1994. (501 calves were sighted in 1997.)

Through Tuesday, about halfway through the peak cow-calf migration period off Central California, Perryman's spotters had counted 192 calves. They expect the number to increase sharply over the next couple of weeks.

"You want to be in the 300s at the end of the season -- those are good calf years," Perryman said.

Gray whale calf production is believed to be relative to the amount of Arctic ice cover during the spring. The cover last spring was sparse, enabling pregnant females early access to important feeding areas.

"In years that ice is slow to melt, primarily in April and May, pregnant females can't get to the feeding grounds," Perryman said. "They're bumping up against this ice trying to get to feeding areas but they can't get far enough north. So when ice is slow to recede the odds of that pregnancies going to term are reduced."

Last year Perryman's spotters counted 255 calves. In 2010 and 2009 they counted only 71 and 86, respectively.

The Pacific gray whale population numbers about 20,000. It has edged upward since extreme mortality events between 1998 and 2000, following poor feeding seasons.

During that period the population suffered a loss of about 10,000 whales, to number about 18,000. Gray whales, which were once hunted to the brink of extinction, were removed from the endangered species list in 1994.